The Second Vatican Council (VC II) was called by Pope John XXIII. Its purpose was pastoral.

The first constitution was Sacrosanctum Concilium - The Constitution on the Sacred Liturgy. In its first paragraph, it defines what the purpose of VC II is:

This sacred Council has several aims in view: it desires to impart an ever increasing vigor to the Christian life of the faithful; to adapt more suitably to the needs of our own times those institutions which are subject to change; to foster whatever can promote union among all who believe in Christ; to strengthen whatever can help to call the whole of mankind into the household of the Church. The Council therefore sees particularly cogent reasons for undertaking the reform and promotion of the liturgy.

In October 11, 1962, VC II opened. The first meeting was attended by 2450 churchmen out of 2908 who were entitled to attend. Thirty-five observers from other Christian churches attended the first meeting and they increased in number in the following sessions. The council lasted four years concluding in 1965.

The first time that Catholics in the United States noticed things were changing was when they went to Sunday Mass and the altar was turned around and the priest was looking at the congregation. How was the world then? The world was in the middle of the Cold War. A major crisis developed from October 16 - October 28, 1962: Cuba and the United States were facing the Missile Crisis. The world came to understand how a foolish decision on the part of a human being could jeopardize humanity. As a civilization, we came to understand how we could be here today gone the next second.

The Second Vatican Council's main documents were four constitutions, nine decrees and three declarations.

Decree On The Up-To-Date Renewal Of Religious LifePerfectae Caritatis, 28 October 1965http://www.vatican.va/archive/hist_councils/ii_vatican_council/documents/vat-ii_decree_19651028_perfectae-caritatis_en.html